The present invention relates to a gas insulation switch suitable for earth anti-warming measures. For example, as described in Engineering Report of Japanese Electrotechnical Committee, No. 552, "Application Guide of Gas Insulation Switch (GIS)" (issued on July 1995), the gas insulation switch (hereinafter called GIS) comprises a single or a plurality of gas insulated units and is installed in a switching station or substation. Each gas insulated unit comprises a grounding steel tank containing high voltage units such as a conductor unit, conductor connection unit, and switching unit and insulating spacers arranged so as to reserve an insulation distance between the high voltage units and the grounding tank, or so as to support the high voltage units, or so as to divide the grounding tank for each gas. As insulating gas, sulphur gas hexafluoride (hereinafter called SF.sub.6 gas) having superior insulation performance and arc extinguishing performance has been used since 1970.